[Chris Jones] "Since I've never set up a RAID before and my budget forces me to set it up myself, I'm a bit nervous to start with something which might prove problematic. "
You should be nervous Chris.
You're dealing hardware that will be at the very heart of your day to day editing operations, and you want it perform in a manner that will provide virtually mission-critical protection, but you're trying to avoid paying the toll to get there.
If you're a professional working with 12Tb of DPX files, you should be charging enough to completely pay for a "proper" professional RAID solution with just 2 to 3 weeks of paid work. If you're not able to fund such a purchase with the work you're doing and the rates you're charging, you have only two alternatives:
1) Raise your rates.
2) Consider a less expensive attached storage solution (not RAID-5).
A properly working hardware-based RAID-5 is terrific, because it will offer vast amounts of storage, high throughput, and some peace of mind. But, having all three of the above comes at a price, and it's the peace of mind that you will lose if you cheap out, either by going it alone, or by buying cheap components, or both.
So, ultimately you're going to have to make a decision to choose what's most important to you: is it storage space and storage speed (throughput), or the peace of mind that only a proper RAID-5 can provide? Only you can answer that question...
David Roth Weiss
ProMax Systems
Burbank
DRW@ProMax.com
http://www.ProMax.com
Sales | Integration | Support
David is a Creative COW contributing editor and a forum host of the Apple Final Cut Pro forum. 
